Purpose:

There is insufficient understanding regarding how generalized OA involving the hand and knee differs from isolated knee OA, which may result from other factors such as obesity or trauma. The purpose of these studies is to determine whether the presence of hand OA involving interphalangeal (IP) and first carpometacarpal (CMC) joints, alone or in combination, predicts progression of patients with symptomatic knee OA.

Methods:

Hand radiographs were obtained on 94 patients at NYUHJD who met ACR criteria for symptomatic knee OA, and who were enrolled in a two-year NIH-sponsored prospective study. The patients completed standardized fixed-flexion knee radiographs at baseline and 24 months, with progression the signal (more painful) knee OA determined by change in joint space width (JSW) and KL score. For these analyses, the patients were separated into two groups by results on their signal knee: 17 progressors, defined by at least 30% decreased JSW over 24 months, and 77 non-progressors. For each set of hand x-rays, 2 radiologists evaluated 18 IP joints and 2 CMC joints for joint space narrowing and/or osteophytes, and whether or not there was erosive change at the IP joints; we averaged the scores from the two readers.

Results:

Kappa scores between the two scoring radiologists for the IP and CMC joints, and for the presence of erosive IP disease, were 0.79, 0.87 and 0.96, respectively. The overall mean IP score was 5.6 and 1st CMC score was 0.9, while medians were 5 and 1.0, respectively. The 17 progressors had a higher average IP (but not CMC) score than the non-progressors, 7.2± 5.4 vs. 5.0±4.6, p=0.13. Since the IP scores were not normally distributed, we further analyzed data by dichotomizing the study populations into two groups using the median IP total (5) as the cutoff point. When so analyzed, the presence of "hand OA" increased the odds ratio of knee OA progression to 2.8 (p=0.096). Of interest, the severity of knee OA correlated with hand OA scores: the average total hand OA scores (out of 20 joints) increased with baseline KL score, with mean scores of 3.8±5.5, 6.1±6.1 and 7.2±5.6 for KL 1 to 3 (p=0.06). There is also an increasing trend of total hand OA joint scores by KL score (p=0.042) when dichotomized around the median (5 joints), and with IP scores alone (p=0.026). The 8 patients with radiographic evidence of erosive IP disease, as compared with the 31 non-erosive IP OA patients (>5 IP joints) and the 54 without IP OA, demonstrated faster knee OA progression over 2 years by average KL increases (1.00, 0.35, 0.30) and decreases in joint space width (0.65, 0.56, 0.36), although perhaps given small numbers, this was not statistically significant (p=0.839).

Conclusions:

In cross-sectional analysis, the quantitative "burden" of hand OA correlates with the radiographic severity of knee OA (KL). Moreover, radiographic hand OA at the IP joints, but not at the 1st CMC joint, predicts more rapid progression of knee OA. Erosive IP disease may be an even stronger predictor than non-erosive IP disease of accelerated progression of knee OA.